FrontendSource - Curated dev & designer resources updated weekly
Invision - Prototyping and collaboration for design teams
Material Up - Curates the best of Material Design inspiration, tools and freebies.
Marvel - Turn sketches, mockups and designs into web, iPhone, iOS, Android and Apple Watch app prototypes.
prototypr.io - Daily design news, inspiration and deals
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.